Alpha-Keto Peracids and Methods For Producing and Using the Same

ABSTRACT

The present invention provides α-keto peracids and methods for producing and using the same. In particular, α-keto peracids are useful as antimicrobial agents.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of U.S. Provisional Patent Application No. 61/199,944, filed Nov. 20, 2008, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to α-keto peracids and methods for producing and using the same.

BACKGROUND OF THE INVENTION

Peracids or peroxyacids as used herein refer to carboxylic acids in which the acidic —OH group has been replaced by an —OOH group. They are strong oxidizing agents and are generally unstable. They are most often used as oxidizing agents in various chemical reactions. Peroxy acids are generally not very stable even in solution and decompose to their corresponding carboxylic acid and oxygen. Because most peracids decompose relatively quickly under ambient conditions, they are typically not used for any other purposes except in chemical reactions. Even then, many peroxyacids are synthesized just prior to their use. Some peroxyacids, for example, meta-chloroperoxybenzoic acid (MCPBA), are somewhat stable at a lower temperature as long as they are not in a pure form. Pure MCPBA can be detonated by shock or by sparks. It is therefore, commercially sold as a much more stable mixture that is less than 72% pure.

Typically, peroxyacids are prepared by electrolytic oxidation of ordinary carboxylic acids or by using a transition metal catalyst and an oxidizing agent or by using a very strong oxidizing agent. In electrolytic oxidation, typically a high current density must be used to form the peroxyacid in good yield. Such use of a high current density typically increase the cost of producing peroxyacids.

As stated above, peroxyacids can also be produced using a transition metal catalyst and an oxidizing agent or simply by using a strong oxidizing agent. Unfortunately, use of a strong oxidizing agent in and of itself creates potentially dangerous conditions and increases the high cost of peroxyacid production. And use of a transition metal catalyst render the resulting peroxyacid often contaminated with the transition metal.

Therefore, there is a need for a safe and economical method for producing peroxyacids.

SUMMARY OF THE INVENTION

Some aspects of the invention provide methods for producing an α-keto peracid. Such methods typically comprise contacting an α-keto carboxylic acid or a salt thereof with an oxidizing agent without any significant stirring and under conditions sufficient to produce the α-keto peracid. While a variety of oxidizing agents can be used in such methods, typically the oxidizing agent comprises hydrogen peroxide, barium peroxide, sodium carbonate peroxide, calcium peroxide, sodium perborate, lithium peroxide, magnesium peroxide strontium peroxide, zinc peroxide, potassium superoxide, or a mixture thereof. In some embodiments, the reaction temperature is about 10° C. or less. In other embodiments, the reaction temperature ranges from about −30° C. to about 10° C.

Methods of the invention can be used to produce a wide variety of α-keto peracids. Some of the useful α-keto carboxylic acids that can be used in methods of the invention include α-keto monocarboxylic acids, α-keto dicarboxylic acids, or a mixture thereof. In some embodiments, the α-keto carboxylic acid comprises pyruvic acid, α-keto butyric acid, α-keto valeric acid, α-keto glutaric acid, 2-oxo cylopental acetic acid, or a mixture thereof.

Other aspects of the invention provide a method for reducing the amount of microbe on a surface, said method comprising contacting the surface with an antimicrobial solution comprising an effective amount of an α-keto peracid. In some embodiments, the α-keto peracid comprises peroxy 2-oxo monocarboxylic acid. In other embodiments, the α-keto peracid comprises peroxy 2-oxo dicarboxylic acid. Still in other embodiments, the α-keto peracid comprises peroxy pyruvate acid, peroxy 2-oxo butyric acid, peroxy 2-oxo valeric acid, peroxy 2-oxo glutaric acid, or a mixture thereof.

Yet in other embodiments, the microbe comprises vegetative bacteria. In other embodiments, the microbe comprises bacterial spores, mycobacteria, gram-negative bacteria, vegetative gram-positive bacteria, or a combination thereof. In one particular embodiment, the microbe comprises bacterial spores.

Still in other embodiments, the antimicrobial solution further comprises hydrogen peroxide. Typically, the antimicrobial solution comprises at least 40 ppm of α-keto peracid. Alternatively, the antimicrobial solution comprises about 4,000 ppm or less, typically 1,000 ppm or less, often 500 ppm or less, more often 100 ppm or less, and still more often 50 ppm or less amount of the α-keto peracid.

The half-life of α-keto peracid in the antimicrobial solution typically is about 120 days or more, often about 180 days or more, and more often about 360 days or more.

Yet other aspects of the invention provide a method for reducing the number of infectious vegetative bacteria on a substrate comprising contacting the substrate with an antimicrobial solution comprising an effective amount of an α-keto peracid. Other aspects of the invention provide a method for reducing the number of bacterial spores on a substrate comprising contacting the substrate with an antimicrobial solution comprising an effective amount of an α-keto peracid.

Further aspects of the invention provide methods for preventing and/or reducing bacteria-related diseases in a mammal that result from the mammal's contact with a bacteria-infected substrate. Such methods comprise contacting the substrate with a composition comprising an α-keto peracid prior to allowing the mammal to come in contact with the substrate.

Still other aspects of the invention provide an antimicrobial product comprising an α-keto peracid. In some embodiments, the product is a household care product. Within such embodiments, in some cases the house hold care product is selected from the group consisting of hard surface cleaners, deodorizers, fabric care compositions, fabric cleaning compositions, manual dish detergents, automatic dish detergents, floor waxes, kitchen cleaners, bathroom cleaners, and combinations thereof. In other embodiments, the antimicrobial product is selected from the group consisting of hard surface cleaners, deodorizers, fabric care compositions, fabric cleaning compositions, manual dish detergents, automatic dish detergents, floor waxes, kitchen cleaners, bathroom cleaners, and combinations thereof. Antimicrobial products of the invention can be used in a wide variety of settings including, but not limited to, in health care facilities such as hospitals, rehabilitation, assisted living facilities, etc.

In other embodiments, the antimicrobial product is a medical device disinfectant. Still in other embodiments, the antimicrobial product is used as a disinfectant for aseptic filling equipment. Yet in other embodiments, the antimicrobial product is used in an aseptic food processing system. In other embodiments, the antimicrobial product is used as a disinfectant for biofilms in water systems. Still in other embodiments, the antimicrobial product is used as a disinfectant for waste water treatment.

In some embodiments, the amount of the peroxy α-keto carboxylic acid present in the antimicrobial product is about 100 ppm or less. Still in other embodiments, the half-life of the peroxy α-keto carboxylic acid is at least 20 days.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows graph of efficacy of peroxy α-keto pyruvic acid against C. Difficile.

DETAILED DESCRIPTION OF THE INVENTION

Some aspects of the invention provide methods for producing α-keto peracids. As used herein, the terms α-keto peracid and α-keto peroxyacid are used interchangeably herein and refer to a compound having a carbonyl group in the α-position (i.e., 2-position) of the peroxyacid group (i.e., —C(═O)OOH group). α-keto peroxyacids of the invention include peroxy α-keto mono- or di-carboxylic acids. The peroxy α-keto dicarboxylic acid include compounds in which either one or two of the acidic —OH groups of the carboxylic group is replaced with the —OOH group. The term α-keto di-peroxyacid refers to a compound having two di-peroxyacid groups in which at least one of the peroxyacid group is adjacent to the carbonyl group.

Some methods of the invention include contacting an α-keto carboxylic acid or a salt thereof with an oxidizing agent without any significant stifling and under conditions sufficient to produce the α-keto peracid. Typically, the reaction condition comprises non-stirring conditions where a mixture of the α-keto carboxylic acid and the oxidizing agent is simply allow to stand without any stirring. As used herein, unless the context requires otherwise, the term “stir” or “stifling” refers to agitating or act of causing a mixing of the reagents by using an external force such as by using a mechanical stirrer, a magnetic stirrer, a shaker, or any other mechanical, electrical, magnetic, or manual force including simply mixing the reagents manually.

Surprisingly and unexpectedly, the present inventors have found that by contacting an α-keto carboxylic acid and an oxidizing agent and letting the mixture stand without any significant mixing, a good yield of the corresponding α-keto peroxyacid can be produced. Generally, the yield of the reaction is at least 5%, typically at least 8%, and often at least 12%.

It should be noted that the yield of the α-keto peroxyacid is affected by a variety of reaction conditions and reagents used. One of the factors influencing the yield of α-keto peroxyacid is the reaction temperature. Generally, the rate of reaction increases as the temperature increases. However, a higher reaction temperature can also increase the yield of side-product(s) and/or decomposition of the α-keto peroxyacid that is formed. Therefore, the reaction temperature is typically kept at about 10° C. or below, often at about 4° C. or below, and more often at about −10° C. or below.

The concentration of the reagents can also affect the rate and the yield of α-keto peroxyacid. The initial concentration of the oxidizing agent is generally about 12 M or less, typically about 7 M or less, and often about 1. M or less. [Ed—I've rounded up these numbers. Let me know if you have different numbers in mind]

The reaction time can also affect the yield of α-keto peroxyacid. Typically the reaction time ranges from about 4 hrs. to about 12 hrs, often from about 6 hrs. to about 8 hrs., and more often from about 10 hrs. to about 12 hrs.

Methods of the invention are applicable to a wide variety of α-keto carboxylic acids. In fact, generally any α-keto carboxylic acid can be used as long as any reactive functional group within the α-keto carboxylic acid is properly protected. Suitable protection groups for various chemical reactions are well known to one skilled in the art. See, for example, Protective Groups in Organic Synthesis, 3rd edition, T. W. Greene and P. G. M. Wuts, John Wiley & Sons, New York, 1999; Smith and March, Advanced Organic Chemistry, 5th ed., John Wiley & Sons, New York, N.Y., 2001; and Harrison and Harrison et al., Compendium of Synthetic Organic Methods, Vols. 1-8 (John Wiley and Sons, 1971-1996), which are incorporated herein by reference in their entirety. Exemplary α-keto carboxylic acids include, but are not limited to, pyruvic acid, α-keto butyric acid, α-keto valeric acid, α-keto glutaric acid, 2-oxo cylopental acetic acid, etc.

Exemplary oxidizing agents that are useful in methods of the invention include, but are not limited to, hydrogen peroxide, barium peroxide, sodium carbonate peroxide, calcium peroxide, sodium perborate, lithium peroxide, magnesium peroxide strontium peroxide, zinc peroxide, potassium superoxide, and the like.

When describing a chemical reaction, the terms “treating”, “contacting” and “reacting” are used interchangeably herein, and refer to adding two or more reagents under appropriate conditions to produce the indicated and/or the desired product. It should be appreciated that the reaction which produces the indicated and/or the desired product may not necessarily result directly from the combination of reagents which were initially added, i.e., there may be one or more intermediates which are produced in the mixture which ultimately leads to the formation of the indicated and/or the desired product.

The reaction is generally conducted in an aqueous solution. Other solvents, such as an organic solvent can also be used in addition to or in place of the aqueous solution. Because it is inexpensive and commercially available in an aqueous solution, typically hydrogen peroxide is used as an oxidizing agent.

The ratio of oxidizing agent to α-keto carboxylic acid typically ranges from about 0.5:1 to about 2:1, often about 2:1 to about 6:1.

While various reaction parameters are disclosed herein, it should be appreciated that the scope of the invention is not limited to these particular reaction parameters.

Utility

While the use of peroxy carboxylic acids as an oxidizing agent in a chemical reaction is generally known, surprisingly and unexpectedly, the present inventors have discovered that α-keto peroxyacids have particularly useful and potent antimicrobial properties. Accordingly, compounds and compositions or the invention can be used as a disinfectant. As used herein, the term “disinfection” refers to removal, destruction, killing, or reducing of at least a significant portion of a pathogenic microorganism population from a surface of an object. Typically, methods, compounds and compositions of the invention can be used to reduce at least about 90%, often at least about 95%, more often at least about 98%, still more often at least about 99.9% and most often all of the microorganism population from a surface. Moreover, in contrast to most commercial antimicrobial compounds that are used as disinfectants, α-keto peroxyacids have been found to be also effective against bacterial spores.

Disinfection is often done to protect the integrity of bacteriological test results (for example, test done for health screening of patients) and/or to prevent the occurrence and spread of disease resulting from inability to control the pathogenic microorganism population. As used herein, the term “microorganism” includes bacteria, virus, fungi, algae, prion, and other pathogenic organisms known to one skilled in the art. Typically, the term microorganism refers to bacteria. Physical sterilization—for example, applying steam or other gas via pressurized autoclave—is generally not feasible for disinfection of large spaces and surfaces or sensitive medical equipment. In addition, physical sterilization is inapplicable for protecting the integrity of test results. Moreover, physical sterilization cannot be used on delicate or temperature-sensitive instruments and devices.

Human and mammalian health is impacted by the spread of microbial entities at home, school, work and in the environment generally. As stated above, conventional methods of disinfection or cleaning and sanitizing various equipments and areas require very high temperatures up to 185° F. or the use of a relatively harsh antimicrobial compound. Unfortunately, the majority of conventional chemical disinfecting agents are useful for reducing only gram-positive bacteria.

Bacteria found on human skin is typically divided into two groups, namely, resident and transient bacteria. Resident bacteria are Gram-positive bacteria that establish as permanent microcolonies on the surface and outermost layers of the skin. Such bacteria play a fundamental role in preventing the colonization of other, more harmful bacteria and fungi. Transient bacteria are bacteria that are not part of the normal resident of the flora of the skin. Rather, transient bacteria are deposited when airborne contaminated material lands on the skin or when contaminated material is brought into physical contact with such bacteria. Transient bacteria are typically divided into two subgroups: Gram-positive and Gram-negative. Gram-positive bacteria include pathogens such as Staphylococcus aureus, Streptococcus pyogenes and Clostridium botulinum. Gram-negative bacteria include pathogens such as Salmonella, Escherichia coli, Klebsiella, Haemophilus, Pseudomonas aeuginosa, Proteus and Shigella dysenteriae. Gram-negative bacteria are generally distinguished from Gram-positive bacteria via the existence of an additional protective cell membrane in the former, which often results in Gram-negative bacteria being less susceptible to conventional, topical antibacterial actives.

As stated above, there exist several compositions and methods for reducing and/or eliminating the formation of bacteria and/or viruses. For example, it is well known that the washing of hard surfaces, food (e.g., fruit or vegetables) and skin, especially the hands, with antimicrobial or non-medicated soap, is effective against viruses and bacteria. Often removal of the viruses and bacteria is due to the surfactant activity of the soap and the mechanical action of the wash procedure, rather than the function of an antimicrobial agent. Thus, it is recommended that people wash frequently to reduce the spread of viruses and bacteria. However, many conventional products and methods of sanitization, including washing, fail to address the dilemma of sanitization “on the go,” that is to say, when a consumer is removed from the benefit of running water. Those skilled in the art have attempted to resolve this dilemma via the incorporation of antimicrobial agents into disinfecting lotions, cleansing wipes and the like. Such articles reduce the need for water during or following the application of the subject composition.

Other conventional antimicrobial cleansing products include deodorant soaps, hard surface cleaners, and surgical disinfectants. These traditional, rinse-off antimicrobial products have been formulated to provide bacteria removal during washing. A few such products, including antimicrobial soaps, have also been shown to provide a residual effectiveness against Gram-positive bacteria, but provide limited residual effectiveness against Gram-negative bacteria. By “residual effectiveness,” it is meant that the antimicrobial agent controls microbial growth on a substrate by either preventing growth of microbes or engaging in continuous kill of microbes for some period of time following the washing and/or rinsing process. To address the dilemma of limited residual efficacy against Gram-negative bacteria, some have sought to incorporate high levels of alcohol and/or harsh surfactants into contemporary antimicrobial products, which have been shown to cause dryness and irritation to skin tissues.

While hundreds of different compounds registered with the EPA, claiming to effectively disinfect or sanitize against various microbes, the vast majority, if not all, of the registered compounds have one or more of the following undesirable characteristics: will leave a residue on the treated surface (which must be wiped away); are flammable (thus, considered a DOT hazard material subject to extra transport and storage restrictions and costs); are corrosive, to some degree, to the surfaces to which they are applied; are toxic to animals (human and non-human); and are, thus, not considered environmentally-friendly; a concept that has been coined in many industries, broadly, as being “Green.” In particular, the following undesirable characteristics have been identified with various currently-used chemical disinfectants: Ethanol and Isopropanol are slow in their germicidal action on surfaces, fairly ineffective against Gram positive bacteria and are not effective against spores. In addition, these are flammable compounds and require one to follow hazardous shipping requirements. Formaldehyde has a pungently irritating odor and is toxic. Phenols, which are basic to a number of popular disinfectants at high dilutions, are toxic, are flammable, and are not effective in ordinary usage against spores. Quartenary ammonium compounds often leave residues, are neutralized by anionic detergents, and are not tuberculocidal or sporicidal even at high concentrations. Hypochlorites are strong oxidizing agents and may function as disinfectants at the proper concentrations, but are, as a whole, corrosive to metals and can be dangerous to handle. Iodophors likewise may function as disinfectants at the proper concentrations, but leave stains (residue) and are often less effective if any appreciable amount of protein is present. Most heavy metal based antimicrobial agents are toxic and more bacteriostatic than bacteriocidal. Peroxides are widely used to clean skin surfaces and wounds, but they have negligible antimicrobial activity.

Microorganisms, including bacteria, fungi, algae, viruses, prions and other such microbial entities, can be found within any growth condition or environment where life exists. While many varieties of bacterial microbes are useful or ‘friendly’ to their animal-hosts, others prove irritating and troublesome—yet, relatively harmless—to manage their populations. Many strains of microbes pose a very serious—and often lethal—risk to the health of co-existent animal populations. Decreasing those troublesome, very serious, and lethal microbial populations under non-sterile conditions requires the use of an antimicrobial agent. Different bacteria show varying degrees of resistance toward a particular disinfectant. Prions tend to be the most-resistant of all microbial entities to antimicrobial agents. Bacterial spores and mycobacteria are generally considered to be the most resistant forms of the bacteria, followed by Gram-negative bacteria, which are generally considered to be more resistant than vegetative Gram-positive bacteria such as the staphylococci and enterococci.

Some aspects of the invention provide antimicrobial compositions and methods for using the same. In some embodiments, the antimicrobial compositions include an α-keto peroxyacid, e.g., peroxy pyruvic acid. Surprisingly and unexpectedly, the present inventors have discovered that such compositions are also effective in disinfecting bacterial spores. Compositions of the invention can optionally include one or more additional antimicrobial agent (e.g., hydrogen peroxide), a pH neutral diluting solvent (e.g., water), or a combination thereof. Typically, the diluting solvent is a pH neutral liquid solvent adaptable for dissolving the α-keto peroxyacid, e.g., water.

Other aspects of the composition can also include an additional agent that can attack the protective protein layer of microbes (for example, non-enveloped viruses or spores) and/or an additional agent that can dissolve the lipid nature of the envelopes or membranes of the microbes. Suitable additional antimicrobial agents include organic acids, peroxides, alcohols, and ethers.

In some embodiments, the concentration of α-keto peroxyacid in solution is about 5,000 ppm or less, typically 1,000 ppm or less, often 500 ppm or less, more often 400 ppm or less, and most often 200 ppm or less. Yet in other embodiments, the composition comprises at least about 2.5% (v/v) of α-keto peroxyacids.

As stated above, compositions of the invention can also comprise a second antimicrobial agent. In some cases, the amount of second antimicrobial agent can be at least 3% (v/v). Suitable second antimicrobial agents include those mentioned herein as well as other antimicrobial agents known to one skilled in the art. In one particular embodiment, the second antimicrobial agent is hydrogen peroxide.

Compositions of the invention can also include one or more of the additional agents. Exemplary additional agents include, but are not limited to, organic acids (such as dichloracetic acid for protein disruption), other peroxides (for protein disruption), alcohols (such as diacetone alcohol for membrane disruption), and ethers (such as butylene glycol monomethyl ether for membrane disruption). Compositions of the invention have shown to be generally non-toxic and non-flammable. Compositions of the invention also evaporate relatively rapidly from a surface-of-interest leaving only an acceptable level of measurable residue.

In some embodiments of the invention, compositions of the invention are used to disinfect a gram-positive bacteria, a gram-negative bacteria, a bacterial spore, or a combination thereof. Unlike other conventionally known antimicrobial agents that are commercially used, compositions of the invention have been shown to be effective in not only disinfecting gram-positive bacteria, but also in gram-negative bacteria, and bacterial spores.

In many instances, compositions of the invention provide at least 6-log order complete kill or reduction of vegetative bacteria when applied to a surface. In other instances, compositions of the invention provide at least 5-log reduction of bacterial spores. Often, compositions of the invention provide a “complete kill” of the bacterial population atop the surface such that any functional bacteria remaining atop the surface-of-interest is/are not capable of re-populating to a measurable level, thereby rendering any toxicity or pathogenic functionality of the original bacterial population effectively null.

Compositions of the invention can be applied in aerosol form such as spraying from a bottle containing liquid antimicrobial agent onto a surface. Once applied to the surface, the composition is adapted to evaporate to dryness (to the touch), typically within about 10 to about 30 minutes while leaving acceptable levels (if any) of measurable residue on the surface, such acceptable levels are generally set based on the surface on which the disinfectant is used. Compositions of the invention are typically non-flammable and of very low toxicity allowing them to be shipped as a non-hazardous chemical, per DOT guidelines. Moreover, solutions comprising the compositions of the invention often have low surface tension and are effective in the presence of proteins.

Compositions of the invention can be used to disinfect clean rooms, hospitals, veterinary and dental offices, laboratories (e.g., general medical/veterinary/dental, Q.A. manufacturing, new product development/R&D, and other laboratories), medical equipments and devices, household surfaces, sports equipments, as well as any suitable objects or surface so desired. Some of the characteristics of compositions of the invention include, but are not limited to, effectiveness at high dilutions in the presence of organic matter; a broad spectrum of antimicrobial activity-effectiveness against gram-positive, gram-negative bacteria, spores, viruses, and fungi); stable under the conditions of transport, storage and use; homogeneity; solubility in water, fats, and oils for good penetration into microorganisms; low surface tension for penetration into cracks and crevices; minimum toxicity-lack of acute and chronic toxicity, mutagenicity, carcinogenicity, etc.; capable of being applied with no residue after a desired period of time has passed; pleasant or minimal odor; non-flammable; low or no impact to plants and animals; and low cost.

Other aspects of the invention provide products that comprise the antimicrobial compositions of the present invention, as well as combinations of such products. Indeed, the combined and systematic use of products containing the antimicrobial compositions of the invention serves to eradicate microorganisms for a longer period of time and prevent their spread.

Some embodiments of the invention provide personal care products comprising the antimicrobial compositions disclosed herein. Suitable personal care products comprising the antimicrobial composition disclosed herein include, but are not limited to, hand soaps, hand sanitizers, body washes, mouth washes, toothpastes, shower gels, shampoos, body lotions, deodorants, nasal sprays, foot care, vaginal care and/or wash, pet care and combinations thereof.

In yet other aspects of the present invention, the personal care products disclosed herein take the form of a wipe product, particularly suitable for wiping or drying the face or hands. In such instance, the antimicrobial compositions of the invention are typically embedded or impregnated into the wipe product.

Still in other aspects of the present invention, the personal care product disclosed herein takes the form of a tissue or towel, also suitable for wiping or drying the face or hands. In another aspect of the present invention, the personal care product takes the form of a feminine napkin and/or a diaper. In another aspect of the present invention, the personal care product takes the form of a first aid antiseptic for irritated, injured, or acne-affected skin and/or for pre or post surgical use.

Yet other aspects of the invention provide antimicrobial compositions disclosed herein that are incorporated into one or more household care products. Indeed, suitable household care products for purposes of the invention include, but are not limited to, hard surface cleaners, deodorizers, fabric care compositions, fabric cleaning compositions, manual dish detergents, automatic dish detergents, floor care compositions, kitchen cleaners or disinfectants, bathroom cleaners or disinfectants and combinations thereof.

In other aspects of the invention, the household care product takes the form of a wipe or towel, suitable for household cleaning and/or care. In some embodiments of the invention, the household care products can comprise certain adjunct ingredients. Exemplary adjuncts include, but are not limited to, detersive enzymes, builders, bleaching agents, bleach activators, transitional metal bleach catalysts, oxygen transfer agents and precursors, soil release agents, clay soil removal and/or anti-redeposition agents, polymeric dispersing agents, brightener, polymeric dye transfer inhibiting agents, chelating agents, anti-foam agents, alkoxylated polycarboxylates, fabric softeners, perfumes, carriers, hydrotropes, processing aids, dyes or pigments, solvents for liquid formulations, solid fillers, detersive surfactants and combinations thereof.

Yet still in other aspects of the invention, the antimicrobial compositions disclosed herein can be incorporated into a skin care product. In such aspects of the invention, the skin care product incorporates a dermatologically acceptable carrier to facilitate safe transfer of the antimicrobial composition disclosed herein to the desired area of the skin. In some embodiments, the skin care product can include certain adjunct ingredients. Suitable adjuncts include, but are not limited to, other antimicrobial and antifungal actives, surfactants, desquamation actives, anti-acne actives, anti-wrinkle actives, anti-atrophy actives, anti-oxidants, radical scavengers, chelators, flavonoids, anti-inflammatory agents, anti-cellulite agents, topical anesthetics, tanning actives, sunscreen actives, conditioning agents, thickening agents, detackifying agents, odor control agents, skin sensates, antiperspirants and mixtures thereof. Other suitable adjunct ingredients are well known to one skilled in the art. See, for example, U.S. Pat. No. 6,294,186, which is incorporated herein by reference in its entirety.

Additional objects, advantages, and novel features of this invention will become apparent to those skilled in the art upon examination of the following examples thereof, which are not intended to be limiting. In the Examples, procedures that are constructively reduced to practice are described in the present tense, and procedures that have been carried out in the laboratory are set forth in the past tense.

EXAMPLES Example 1

This example illustrates one method of testing the antimicrobial effects of compounds of the invention.

Kill Time Test

This is a test performed to demonstrate log reduction values over time for a disinfectant against selected bacteria, fungi, and/or mold. A representative list of the organisms tested include, but are not limited to, Bacillus subtilis, Bacillus atrophaeus, Bacillus thuringiensis, Staphylococcus aureus, Salmonella cholerasuis, Pseudomonas aeruginosa, Aspergillus niger, and Trichophyton mentagrophytes. The following exemplifies one procedure derived from disinfectant test methods found in guidelines of the Association of Official Analytical Chemists (AOAC) to meet “log reduction criteria” established by the U.S. Environmental Protection Agency (EPA) and U.S. FDA for certain applications: (1) A tube of the sample-disinfectant is placed into a waterbath for temperature control and allowed to equilibrate; (2) Once the tube has reached temperature, it is inoculated to achieve a concentration of approximately 10⁶ CFU/mL; (3) At selected time points (generally five points are used including zero) aliquots are removed and placed into a neutralizer blank; (4) Dilutions of the neutralizer are made and selected dilutions plated onto agar; (5) Colonies are enumerated and log reductions are calculated.

Preparation of Bacterial Suspensions

In order to obtain observable significant reductions (on the order of 10⁶) of surface bacteria, a high number of viable CFU/in² must be available for treatment on the surface to be disinfected. Since a substantial number of organisms die during the drying process, it is necessary to start with bacterial suspensions that exceed the concentration desired on the final surface. It has been found that a suspension prepared from an agar plate that has been stored refrigerated over-night yields a relatively even surface film upon application and drying. The cool overnight storage of the agar plate reduces the surface tension of the subsequent suspension. Suspensions were prepared in sterile skim milk medium (SM) by harvesting the organism from the agar plate using a sterile cotton swab and vigorously vortex mixing to achieve homogeneity. A viable concentration of 10⁸-10⁹ CFU/mL was used. Most non-fastidious organism suspensions can be retained in the cooler for several days, and were used as long as enumeration demonstrated satisfactory viability.

Test Surface Preparation

Glass cover slips (e.g., 25 mm²) were used as the test surface for this procedure. Sterile slides were used for this procedure. Slides were sterilized by placing them in layers separated by filter paper (e.g., Whatman #1) and placing them in an aluminum envelope then baking at 150-170° C. for 1-2 hours.

The microorganism film was prepared by dispensing 20 μL of suspension onto a sterile slide and spreading the suspension drop over the surface of the slide. A sterile inoculating needle that has been bent in the shape of a hockey stick was used. The slide were placed on the pins of a sterile disposable plastic 96 well inoculating head that had small drops of sterile water placed onto some of the pins to help hold the slide in place during preparation. The suspension was spread as near to the edges of the slide as possible without touching the edge. The drop was respread once more when necessary without over spreading. The suspension was allowed to dry uncovered at room temperature. Inoculated slides were used as soon as possible, often the same day to minimize loss of viability.

Disinfectant Application

Care was taken during treatment application to assure consistency between slides and experiments. Disinfectants were applied to inoculated slides with an air brush (e.g., Iwata revolution R4500) from a distance of 20-30 cm and a 12-18 psi setting of the compressor output regulator. Travel time for a treatment pass was about 1 ft/sec. Methods were adjusted in order to maintain consistent application between slides. Slides were air dried uncovered at room temperature.

Enumeration

The effectiveness of treatments was evaluated by enumeration of the surviving bacteria on the slide. The bacteria were removed from the slide and the disinfectant was neutralized by immersion of the slide in Letheen broth (LB). The bacteria were then plated in appropriate dilutions. A positive control was included for comparison to assess efficacy.

To enumerate viable organisms on a slide, the slide was placed into a 50 mL centrifuge tube containing 20 mL of LB. The tube was vigorously shaken for 5 seconds and then vortexed for 5 seconds. Mixing step was repeated once. The LB was diluted in peptone, and was plated on an appropriate agar to attain countable dilutions. The LB tube (for decreased limit of quantitation) and agar plates were incubated overnight at the appropriate atmosphere and temperature.

Typically, for an effective disinfectant, about 50 μL of the LB tube was logarithmically spiral plated (DF=20) onto the appropriate agar. In some cases, LB was plated at higher dilutions, e.g., transferred 90 μL of LB to 9 mL of peptone and spiral plated 50 μL (DF=2000).

The CFU/slide was calculated using the spiral plater counting tables and multiplying by the dilution factor. Viability loss due to disinfection was determined by comparing treated slide values with the untreated positive control.

Example 2

Various concentrations of peroxy pyruvic acid generated from different compositions of a mixture from pyruvate, hydrogen peroxide (H₂O₂), and water were tested to determine the log reduction of Bacillus cereus spores. These spores had been incubated for 7 years and thus the possibility of vegetative cells remaining was very low. Each sample of dilute pyruvate and hydrogen peroxide solution noted in Table 2 was tested employing the spray test outlined above. Slides of MRSA were treated with peroxy pyruvic acid derived from the composition of 10% pyruvate and 3% H₂O₂ as a control. The log reduction of the MRSA control was approximately 6-logs, there was no growth in the broth used to plate for enumeration, therefore, it was assumed that complete elimination of the MRSA population was accomplished. As Table 2 illustrates, peroxy pyruvic acid derived from a mixture of 10% pyruvate with 3% H₂O₂ resulted in a 3.5-log reduction of the B. cereus spores. However, peroxy pyruvic acid derived from the composition of 5% pyruvate and 3% H₂O₂ eliminated all the B. cereus spores. As in Example 1 above, the water used in these studies is USP purified.

TABEL 2 Log Reduction of Bacillus cereus spores. Positive B. cereus Control (BC 2) log = 5.7 Positive MRSA Control (Sta 25) log = 8.3 Solution No. Organism % H₂O₂ % Pyruvate Log Reduction 2 MRSA 3 10 >5.7* 1 BC 2 1 10 1.1 2 BC 2 3 10 >3.5 3 BC 2 1 5 0.4 4 BC 2 3 5 5.7* 5 BC 2 — 10 1.1 6 BC 2 — 5 0.8 *Total kill/destruction of microbes, i.e. no growth in Letheen broth tubes (3 reps).

Example 3

Peroxy pyruvic acid was synthesized as follows. Pyruvic acid was added to hydrogen peroxide at a temperature of between −30° C. and 10° C. until a conglomerate layer formed on the bottom of the flask. The reaction was allowed to stand without stifling until all pyruvic acid had dissolved into solution. Formation of peroxy pyruvic acid was confirmed by mass spectrometer and by chemical reaction.

Example 4

The reaction of Example 3 was repeated with the addition of Sulfuric Acid (H₂SO₄) as a catalyst. An ice bath was used to keep the reaction cool resulting in quantifiable amounts of perpyruvic acid production.

Example 5

Reaction of Examples 3 and 4 were repeated for α-Ketobutanoic Acid (CH₃CH₂COCOOH) and α-Ketovaleric Acid (CH₃CH₂CH₂COCOOH) to produce the corresponding α-keto peracids.

Example 6

FIG. 1 shows efficacy of peroxy pyruvic acid against C. Difficile using sulfuric acid catalysts and methods of Example 1 above. All efficacy studies for C difficile were done according to the Official Method 966.04 “Sporicidal Activity of Disinfectants”

FIG. 2 shows efficacy of peroxy alpha keto butyric acid against C. Difficile.

Example 7

In another experiment, 15 ml of 30% Hydrogen Peroxide was stirred using a stir bar while adding 0.25 ml of the Pyruvic acid in increments every 1.5 minutes. In one instances, the reaction was carried out at room temperature and in another instances at 5° C. Titration of the resulting mixtures showed that there was no observable peracid formation.

The foregoing discussion of the invention has been presented for purposes of illustration and description. The foregoing is not intended to limit the invention to the form or forms disclosed herein. Although the description of the invention has included description of one or more embodiments and certain variations and modifications, other variations and modifications are within the scope of the invention, e.g., as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative embodiments to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter. 

1. A method for producing an α-keto peracid comprising contacting an α-keto carboxylic acid or a salt thereof with an oxidizing agent without any significant stifling and under conditions sufficient to produce the α-keto peracid.
 2. The method of claim 1, wherein the oxidizing agent comprises hydrogen peroxide, barium peroxide, sodium carbonate peroxide, calcium peroxide, sodium perborate, lithium peroxide, magnesium peroxide strontium peroxide, zinc peroxide, potassium superoxide, or a mixture thereof.
 3. The method of claim 1, wherein the reaction temperature is about 10° C. or less.
 4. The method of claim 1, wherein the reaction temperature ranges from about −30° C. to about 10° C.
 5. The method of claim 1, wherein the α-keto carboxylic acid comprises an α-keto monocarboxylic acid.
 6. The method of claim 1, wherein the α-keto carboxylic acid comprises an α-keto dicarboxylic acid.
 7. The method of claim 1, wherein the α-keto carboxylic acid comprises pyruvic acid, α-keto butyric acid, α-keto valeric acid, α-keto glutaric acid, 2-oxo cylopental acetic acid, or a mixture thereof.
 8. A method for reducing the amount of microbe on a surface, said method comprising contacting the surface with an antimicrobial solution comprising an effective amount of an α-keto peracid.
 9. The method of claim 8, wherein the α-keto peracid comprises peroxy 2-oxo monocarboxylic acid.
 10. The method of claim 8, wherein the α-keto peracid comprises peroxy 2-oxo dicarboxylic acid.
 11. The method of claim 8, wherein the α-keto peracid comprises pyruvate peracid, peroxy 2-oxo butyric acid, peroxy 2-oxo valeric acid, peroxy 2-oxo glutaric acid, or a mixture thereof.
 12. The method of claim 8, wherein the microbe comprises vegetative bacteria.
 13. The method of claim 8, wherein the microbe comprises bacterial spores, mycobacteria, gram-negative bacteria, vegetative gram-positive bacteria, or a combination thereof.
 14. The method of claim 8, wherein the antimicrobial solution further comprises hydrogen peroxide.
 15. The method of claim 8, wherein the antimicrobial solution comprises at least 40 ppm of α-keto peracid.
 16. A method for reducing the number of infectious vegetative bacteria on a substrate comprising contacting the substrate with an antimicrobial solution comprising an effective amount of an α-keto peracid.
 17. A method for preventing and/or reducing bacteria-related diseases in a mammal that result from the mammal's contact with a bacteria-infected substrate, said method comprising contacting the substrate with a composition comprising an α-keto peracid prior to allowing the mammal to come in contact with the substrate.
 18. An antimicrobial product comprising an α-keto peracid.
 19. The antimicrobial product of claim 18, wherein said product is a household care product.
 20. The antimicrobial product of claim 19, wherein said house hold care product is selected from the group consisting of hard surface cleaners, deodorizers, fabric care compositions, fabric cleaning compositions, manual dish detergents, automatic dish detergents, floor waxes, kitchen cleaners, bathroom cleaners, and combinations thereof.
 21. The antimicrobial product of claim 18, wherein said product is selected from the group consisting of hard surface cleaners, deodorizers, fabric care compositions, fabric cleaning compositions, manual dish detergents, automatic dish detergents, floor waxes, kitchen cleaners, bathroom cleaners, and combinations thereof.
 22. The antimicrobial product of claim 18, wherein said product is a medical device disinfectant.
 23. The antimicrobial product of claim 18, wherein said product is used as a disinfectant for aseptic filling equipment.
 24. The antimicrobial product of claim 18, wherein said product is used in an aseptic food processing system.
 25. The antimicrobial product of claim 18, wherein said product is used as a disinfectant for biofilms in water systems.
 26. The antimicrobial product of claim 18, wherein said product is used as a disinfectant for waste water treatment.
 27. The antimicrobial product of claim 18, wherein the amount of said peroxy α-keto carboxylic acid present in said product is about 100 ppm or less.
 28. The antimicrobial product of claim 18, wherein the half-life of said peroxy α-keto carboxylic acid is at least 20 days. 